This invention is directed toward improved compositions and methods relating to methods of stabilizing nuclear materials including weapons grade materials such as U or Pu fluorides, chlorinated oxides, so-called “non MOXables and mixed waste previously described and disclosed in the following U.S. patents, the disclosures of each of which are herein incorporated herein by reference, U.S. Pat. No. 5,645,518, Method for Stabilizing Low-Level Mixed Wastes at Room Temperature, Assigned to Univ. Chicago, Inventors: Arun S. Wagh and Dileep Singh (1997); U.S. Pat. No. 5,830,815, Method of Waste Stabilization via Chemically Bonded Phosphate Ceramics, Assigned to Univ. Chicago, Inventors: Arun S. Wagh, Dileep Singh, and Seung Young Jeong (1998); U.S. Pat. No. 6,153,809, Polymer Coating for Immobilizing Soluble Ions in a Phosphate Ceramic Product, assigned to US Department of Energy, Inventors: D. Singh, A. Wagh, and K. Patel (2001); U.S. Pat. No. 6,133,498, for Method for Producing Chemically Bonded Phosphate Ceramics and for Stabilizing Contaminants Encapsulated Therein Utilizing Reducing Agents From An Aqueous Solution, Assigned to US Department of Energy, Inventors: D. Singh, A. Wagh, and S. Jeong (2001); and U.S. Pat. No. 6,204,214, Pumpable Injectable Phosphate-Bonded Ceramics, Assigned to Univ. Chicago, Inventors: D. Singh, A. Wagh, L. Perry, and S. Jeong (1998).
In accordance with a treaty between Governments of United States and Russia, disposition of Pu and other actinides or transuranics (TRUs) must conform to the Spent Nuclear Fuel (SNF) standard to make it unattractive to proliferators. The SNF standard requires that Pu, U and possibly other actinides such as AM or TRUs be as difficult to recover from any form as it would be to recover from SNF. The current DOE-proposed method is for plutonium to be first stabilized and solidified in a solid matrix, then encapsulated in glass containing radioactive components such as fission products, and stored in facilities such as proposed at Yucca Mountain in the United States and a similar facility in Russia. Such disposition has come to be known as DOE's Immobilization Program for weapons-grade and non-weapons grade excess nuclear material. This invention relates to a method of stabilization and solidification—immobilization—of actinides and/or TRUs more safely and efficiently than the current DOE-proposed method, and the product produced thereby.
Facilities for processing actinides, especially plutonium, to meet the SNF are not available at this time. Therefore, to meet U.S. Nuclear Material Disposition requirements, certain Pu and Pu-bearing compounds must be stabilized and packaged to meet current shipping and long-term, i.e., up to 50 years, storage requirements. These requirements, targeted at eliminating hydrogenous components in the material, including moisture, are designed to minimize H2 generation and associated pressure build-up over time in the shipping and storage containers. They are also designed to minimize the presence of moisture that may compromise the criticality potential of the materials and to minimize corrosives such as halogenated compounds that may compromise the integrity of the container. The DOE 3013 Standard specifies stabilization process and container technology for meeting these objectives. This invention addresses a method of stabilization and solidification, as well as the product, to meet the performance objectives—safe storage—of the 3013 Standard more safely and efficiently.
Nuclear materials in the US Department of Energy Complex in the United States, Former Soviet Union (FSU) countries, and other nuclear countries in the world exist in various forms. These may be as oxides, halides (such as fluorides, chlorides), chlorinated oxides, other salts, or in acids. Furthermore, there exist various organic chemicals contaminated by actinides and/or TRUs, such as oils, greases and solvents. There is a need for a stabilization technology that will treat this range of materials effectively to meet not only the immobilization and stabilization/safe storage standards cited above but also the Waste Isolation Pilot Plant Waste Acceptance Criteria (WIPP-WAC). This invention also provides a method for producing monoliths of actinides and/or TRU/mixed wastes (e.g., ash, slag, oxides, chloride, fluoride, organics, other salts, or acids) that would minimize H2 and volatile organic compounds (VOC) generation, resist/reduce Pu recoverability to meet Safeguards Termination Limits (STL) performance objectives, and would not be dispersive. The invention, provides methods as well as the products, of producing ceramic monoliths at room temperatures or at slightly elevated temperatures where volatilization of components does not occur. Once formed and heated at low temperatures (to eliminate water), these ceramic monoliths could be safely shipped and stored without pressure build-up concerns, and could also be heat treated to high temperatures and encapsulated in molten glass without affecting their integrity or without concerns of off-gases.
Even for low-level and non-radioactive organic hazardous waste treatment applications, there is a need for a low-temperature stabilization technology. The conventional approach in disposal of contaminated oils, greases, and other organics is to destroy them by some pre-treatment method, e.g., pyrolysis, and then stabilize the ash resulting from the pyrolysis. The off-gas from this operation, however, may be contaminated by hazardous contaminants and hence this method is both costly and opposed by many communities.
Earlier Stabilization and Immobilization (S/I) technologies for S/I for TRU nuclear material or waste disposition include: heating to eliminate H2O and organics, then sealing in welded shipping and containers; ceramification, including SYNROC; cementation, including FUTAP cements; sorption in fly ash, including Gubka technology; or vitrification. While there are serious concerns of hydrogen generation with hydrated cements, ceramification and vitrification require high temperature treatment. If the waste streams contain volatile or corrosive compounds, e.g., containing latent moisture, fluorides, chlorides, or organics, their high temperature treatment poses off-gassing issues and also interferes with formation of a monolithic ceramic or glass. Cost of these processes and generation of secondary waste streams such as contaminated furnaces, etc., are major issues.